Method and apparatus for individualizing fibers preparatory to web forming



Dec. 9. 1969 H. M. FLEWWELLING 3,482,237

METHOD AND APPARATUS FOR INDIVIDUALIZING FIBERS PREPARATORY T0 WEBFORMING Filed Nov. 8, 1967 INVENTOR Herbert Martin FLEWWELLING UnitedStates Patent METHOD AND APPARATUS FOR INDIVIDUALIZ- lNG FIBERSPREPARATORY TO WEB FORMING Herbert Martin Flewwelling, Pointe Claire,Quebec, Canada, assignor to Domtar Limited, Montreal, Quebec, Canada, acompany of Canada Filed Nov. 8, 1967, Ser. No. 689,214 Claims priority,application Canada, Oct. 10, 1967,

Int. Cl. D01g 255/00; D04h 17/00 US. Cl. 19156.3 9 Claims ABSTRACT OFTHE DISCLOSURE A head, primarily for individualizing and dry laying offibers or similar materials, said head having a recirculaton path alongwhich said materials are carried in an air stream, said path having ashape resembling an oval but with an outwardly concave classificationsection formed in one of the longer sections of the path and an outletthrough the outer wall of said path in said concave section ahead of thecrest of said concave section in the direction of movement of saidmaterial.

provide a system for separating fibers and laying same in the form of aweb. The present invention can be used as a device for separating fibersper se or for laying fibers or for both separating and laying of fibers.

The present invention may also be utilized for materials other thanfibers, for example fibrids, powders or mixtures thereof (i.e. apowdered adhesive and fibers to form an adhesive bonded fiberboard) oreven with different shaped particles such as flakes or the like.

Broadly the present invention comprises a circulation path having aninner and an outer wall, means to introduce a transporting fluid intosaid path as a jet, said transporting fluid acting to separate saidmaterial and to transport same around said path, at least one sectionconcave to said outer wall in said path, means in said concave sectionahead of the crest of said section in the direction of travel of saidmaterial to permit said material together with transporting fluid toleave said path through said outside wall.

The apparatus of the present invention broadly comprises a confined pathhaving an inside and an outside wall, a dispersion section, a convexcurved positioning section and a concave curved classification sectionin series along said path, means causing fluid to flow in said confinedpath and to entrain said material, said curved positioning section beingshaped to cause said material to move toward and hug said outside walland said classification section being curved to separate said materialsinto a retained and a discharge fraction, a discharge duct through saidoutside wall and positioned to discharge said discharge fraction fromsaid path.

Further features, objects and advantages will be evident from thefollowing detailed description taken in conjunction with theaccompanying drawings in which:

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FIG. 1 is a sectional view to scale through one form of the invention.

FIG. 2 is an end view of the apparatus shown in sec tion in FIG. 1.

The apparatus of the present invention comprises a circuitous path orduct 12 defined by an outer wall 14 and an inner wall 16 and a pair ofend walls 18. In the illustrated embodiment, the end walls 18 aresubstantially parallel. The duct 12 has a dispersion zone 20 and anouter concave section or classification zone 22, a positioning zone orbend 24 interconnecting one pair of adjacent ends of the dispersion andclassification zones, and a return bend 26 interconnecting the oppositeends of said zones. Both the positioning and return bends extend on anarc of greater than about in the illustrated arrangement. The size andshape of the positioning bend 24 affects the operation of the apparatusas will be more clearly explained hereinbelow. The path or duct 12resembles an ellipse with one of its sides moved in towards the centerto form a concave curved outer section as illustrated at 22.

A material inlet 28 is provided, preferably at the beginning of thedispersion zone 20 adjacent the bend 26. A fluid jet 27 mounted to therear of the inlet 28 injects fluid (air) at high velocity into the ductor path 12, and this fluid serves as the dispersing and transportingmedium for the material entering the path 12. The shear forces in thefluid may cause the material to be separated into smaller segments as itis dispersed. The angle of the inlet jet, the pressure, and the volumemay be varied to provide different velocities and turbulences for thedispersion and circulation of the material. A discharge zone or duct 30is provided in the outer wall 14 towards the end of the concaveclassification section 22 adjacent the return bend 26, i.e. at a pointin advance of the crest of lthe section 22 in the direction of travel ofthe materia The dispersion zone 20, positioning zone 24, classificationzone 22 and discharge zone 30 are the basic elements of the inventionand the inter-relationship of the classification zone and discharge zone30 are of primary importance to the practice of the instant invention.

Preferably, but not essentially, a second high velocity jet 32 isprovided at the end of the positioning section 24 and is directedtowards the beginning of the concave section 22. This jet 32 acceleratesand redirects the material being processed thereby further dispersingand separating the material into smaller segments and positioning thematerial to facilitate proper classification in the concave section 22.The jet 32 preferably is adjustable in the same manner as the inlet jet27 referred to above.

The discharging material is received and held in position on a suitablecollecting surface. In the illustrated embodiment the collecting surfaceis formed by a foraminous belt 34 and the material is held in positionby a suction box 38 provided on the side of the belt 34 remote from theduct 30. Transporting fluid is drawn through the belt 34 into thesuction box 38 to deposit and fix the material in position on the belt.

As shown, particularly in FIG. 2, the width (i.e in the cross-machinedirection) of the duct or path 12 may be, and preferably is, maintainedsubstantially constant and equal in width to the mat to be formed onbelt 34. Maintaining the path 12 substantially equal in width to the matpermits a more uniform lateral distribution of material. In theillustrated embodiment the duct 30 is shown as having substantially fiatend walls which are merely extensions of the end walls 18 of the path12, while the front and rear walls are flared slightly in the directionof movement of the belt 34. The end walls may also be flared slightlylaterally if desired.

As above indicated, the transverse width of the path 12 is substantiallyconstant and equal to the width of the mat to be formed, but the heightof the path 12 may be varied thereby changing the cross-sectional areaof the path and the velocity of the circulating fluid and material. Thesurfaces of the outer and inner walls 14 and 18 respectively facing thepath 12 are flat in transverse cross-section as shown in FIGS. 1 and 2.

In operation, material, such as wood pulp, is introduced into theapparatus through inlet 28, While high velocity fluid (air) isintroduced through the jets 27 (and 32 if used) and air entrained pulpis removed via the outlet 30. The air flow through the apparatus causesa slight suction force on the inlet 28 which induces flow into the ductthrough this inlet. As the pulp enters the duct 12 it is entrained inthe air flow and traverses the dispersion zone 20 where bundles offibers are separated and the fibers dispersed by turbulence in the airstream. Next, the pulp travels through the positioning zone or bend 24,which is designed to cause the pulp to move into hugging engagement withthe outside wall 24 where it remains until it enters the externallyconcave classification zone or section 22. As the pulp traverses thiszone 22 it is acted upon by forces (i.e. centrifugal force, shear force,etc.) inherent in the flow in the classification section, which forcescause certain particles, e.g. fiber bundles or clumps of fibers notsufliciently broken down into individual fibers, to approach the innerwall quicker than other particles, e.g. the pulp which has beensufiiciently broken down. The outlet duct 30 is positioned relative tothe concave classification section 22 to divide the flow into twoseparate fractions, namely a discharge fraction and a retained fraction.The discharge fraction contains only that pulp broken up to the requireddegree, while the retained fraction includes pulp not sufficientlybroken up to be discharged (i.e. the fiber bundles). The dischargefraction leaves the duct 12 through the outlet duct 30 as asubstantially laterally uniform dispersion of fibers, while the retainedfraction traverses the return bend 26 and is further subjected to theturbulent air which further reduces the fiber bundles and thiscirculation continues until the fiber bundles are broken down to therequired size for discharge.

By positioning the discharge duct 30 at a point on a concaveclassification zone 22 of predetermined curvature and by controlling thevelocity of the material through this zone 22, the relationship (i.e.quantitative ratio, composition, etc.) between the retained anddischarge fractions may, to some extent, be varied.

The function of jet 32 if used, is mainly to accelerate the pulp toensure that it enters the classification zone 22 with the propervelocity and to aid in properly positioning the pulp in huggingrelationship with the outside wall 14.

The quantity of air added, the size of the duct 12, the shape of theducting, the density, size and shape of the material all contribute indetermining the velocity of the material and the forces acting thereon.Thus, the exact configuration of the apparatus and the exact jetvelocities and quantities of air will vary with various materials andresults desired. When the fibers are to be laid to form a mat it isimportant to introduce suflicient air so that the volume of air exitingthrough the duct 30 permits the fibers to leave as substantiallynon-contacting individual integers.

The above described example of the instant invention has primarily dealtwith pulp fibers and FIG. 1 is a drawing to scale of the first model ofthe invention, and has been found suitable for use with wood pulpfibers. The actual dimensions of the duct 12, and the curvature of thepositioning bend 24, and classification zone 22, and discharge duct 30,can all be altered to adapt the characteristics of the device foroptimum results with a given material to be processed. As aboveindicated, the present invention is not to be limited to use with fibersor to the exact specific shape disclosed.

Similarly, only air has been referred to as the fluid medium, however,other fluids may also be used provided they permit the requiredpositioning and classification of the material. Also the fluid may serveother functions than for separation and conveying of the material, suchfunctions including treating, drying and otherwise affecting thecharacteristics of the fibers.

Modifications may be made to the invention as disclosed withoutdeparting from the spirit of same as defined in the appended claims.

What is claimed is: 1. An apparatus for separating material comprisingmeans including an inside and an outside wall defining a continuousconfined circuitous path having its longitudinal center line lying in aplane and including in series a dispersion section, a convex curvedpositioning section connected directly to a concave curvedclassification section, means defining an inlet for introducing saidmaterial into said path without disrupting the operation of saidpositioning and classification sections, jet means for introducingentraining fluid into said path, said dispersion section beinginterposed between said jet means and said convex curved positioningsection, and means defining a discharge duct opening through saidoutside wall in said classification section on the side of the crest ofsaid concave curved classification section remote from said positioningsection.

2. An apparatus as defined in claim 1 further comprising; fluidinjecting means for introducing fluid into said duct adjacent thejunction of said positioning section with said classification section.

3. An apparatus as defined in claim 1 wherein the surface of saidoutside wall facing said path in said convex curved positioning sectionand said concave curved classification section is substantially flat intransverse crosssection.

4. An apparatus for laying materials to form a mat comprising; meansincluding curved inner and outer walls defining a continuous, confined,circuitous path having its longitudinal center line in a plane andincluding in series a dispersion section and a convex curved positioningsection connected directly to a concave curved classification section,means defining an inlet for introducing said material into said pathwithout disrupting the operation of said positioning and classificationsections, the surface of said outside wall facing said path in saidconvex curved positioning section and said concave curved classificationsection being substantially flat in transverse cross-section, jet meansto introduce fluid into said path, said dispersion section of said pathbeing interposed between said jet means and said convex curvedpositioning section, means defining a discharge duct opening throughsaid outside wall in said classification section on the side of thecrest of said classification section remote from said positioningsection, a receiving surface positioned across said duct and meansmounting said receiving surface from movement across said duct.

5. An apparatus as defined in claim 4 further comprising; second meansto introduce fluid, said second means being located adjacent thejunction of said positioning and classification sections.

6. A method of forming a uniform web from material having fiber bundlestherein comprising;

introducing said material including said fiber bundles into a confinedpath between an inside and an outside wall which define a dispersionsection, a convex curved positioning section and a concave curvedclassification section having a crest therein in said path, said pathhaving its longitudinal center line in a plane,

controllably introducing conveying fluid into said path at the end ofsaid dispersion section remote from said positioning section at a ratewhereby turbulence is generated in said dispersion section to tend toseparate said fiber bundles and to generate a fluid velocity in saidpath sufficient to entrain said material and move said material throughsaid path at a velocity to permit centrifugal positioning andclassification of said material in said positioning and classificationsections,

withdrawing a fraction of said material substantially free of said fiberbundles through said outside wall in said classification section on theside of said crest remote from said positioning section,

continuously collecting said withdrawn fraction in the form of asubstantially flat web, and

recirculating said material including fiber bundles not sufficientlydispersed and fluid not withdrawn from said classification section backto said dispersion section.

7. A method as defined in claim 6 wherein said fluid is air.

8. A method as defined in claim 7 further comprising introducing furtherfluid into said path adjacent the junction of said positioning andclassification sections at a rate suflicient to increase the velocity ofsaid material through said classification section.

References Cited UNITED STATES PATENTS Stephanoff 2415 Step-hanoff 2145Stephanofl. 24139 X Boesch 209143 Meiler 19156.3

Oja 19156.3 Kidwell 24139 Novotny 19200 FRANK W. LUTTER, PrimaryExaminer US. Cl. X.R.

